From: Matt Redfearn <matt.redfearn@xxxxxxxxxx> This patch has been added to the 4.1 stable tree. If you have any objections, please let us know. =============== [ Upstream commit 8f46cca1e6c06a058374816887059bcc017b382f ] This patch fixes the possibility of a deadlock when bringing up secondary CPUs. The deadlock occurs because the set_cpu_online() is called before synchronise_count_slave(). This can cause a deadlock if the boot CPU, having scheduled another thread, attempts to send an IPI to the secondary CPU, which it sees has been marked online. The secondary is blocked in synchronise_count_slave() waiting for the boot CPU to enter synchronise_count_master(), but the boot cpu is blocked in smp_call_function_many() waiting for the secondary to respond to it's IPI request. Fix this by marking the CPU online in cpu_callin_map and synchronising counters before declaring the CPU online and calculating the maps for IPIs. Signed-off-by: Matt Redfearn <matt.redfearn@xxxxxxxxxx> Reported-by: Justin Chen <justinpopo6@xxxxxxxxx> Tested-by: Justin Chen <justinpopo6@xxxxxxxxx> Cc: Florian Fainelli <f.fainelli@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx # v4.1+ Cc: linux-mips@xxxxxxxxxxxxxx Patchwork: https://patchwork.linux-mips.org/patch/14302/ Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx> --- arch/mips/kernel/smp.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c index 3cef551..a0268f61 100644 --- a/arch/mips/kernel/smp.c +++ b/arch/mips/kernel/smp.c @@ -172,6 +172,9 @@ asmlinkage void start_secondary(void) cpumask_set_cpu(cpu, &cpu_coherent_mask); notify_cpu_starting(cpu); + cpumask_set_cpu(cpu, &cpu_callin_map); + synchronise_count_slave(cpu); + set_cpu_online(cpu, true); set_cpu_sibling_map(cpu); @@ -179,10 +182,6 @@ asmlinkage void start_secondary(void) calculate_cpu_foreign_map(); - cpumask_set_cpu(cpu, &cpu_callin_map); - - synchronise_count_slave(cpu); - /* * irq will be enabled in ->smp_finish(), enabling it too early * is dangerous. -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html